Thermal transport across epitaxial NiAl_1-xGa_x/GaAs interfaces

While the topic of thermal interface conductance is widely studied, there are still just a few studies of transport across epitaxial metal-semiconductor interfaces, and thus reliable benchmark data for atomistic computational tools remains scarce. NiAl and NiGa are good metals with simple cubic lattice structures of nearly identical lattice constant (a=2.88 A), nearly half of that of GaAs. We report the epitaxially growth of NiAl_1-xGa_x on GaAs (a=5.65 A) across the entire compositional range, x, for 12 different alloy compositions as well as measurements of their thermal interface conductance over a wide range of temperatures (77-700K). The results are compared to several theoretical models of electron/phonon transport coupled to first-principles calculations. In particular, we find that phonon-only models of transport dramatically overestimate the observed conductance. Calculating the electron-phonon coupling parameters and lattice thermal conductivity of the metals using first-principles calculations, we show that these effects must be accurately included to capture the observed transport observations.